The Truth About Primer Misfires - Guns & Ammo article review

[LiveLife]

Came across this Guns & Ammo article on primer misfires that will supplement our discussion on primers - https://www.gunsandammo.com/editorial/the-truth-about-primer-misfires/247980

BTW, THR thread on primer misfire - https://www.thehighroad.org/index.p...-and-discussions.778197/page-10#post-11386382

US Army AMU on primer seating - https://www.thehighroad.org/index.p...-and-discussions.778197/page-10#post-11403561


G&A article covered primer construction (cup, anvil, and priming compound called "pellet") and operation (When cup is hit, indent from firing pin/striker tip ignites priming compound against the anvil tip)

Interesting thing I noticed from the article was the reliability of primers.

"Based on the SAAMI-specified drop test, statistics will tell you that our [Winchester] primers are 99.9997 percent reliable ... A lead-styphnate primer is probably one of the oldest and most reliable devices on the planet."​

Article noted that Black Hills Ammunition (Which uses Winchester primers) who test fires more than 100,000 rounds per year and sells tens of millions of rounds each year, their investigations over the years identified misfires were the result of a defective primer in only a very small number of cases.

"Primers are not perfect — nothing man-made is — but they are very reliable. Statistically, you might encounter a defective primer, if you shoot enough ... 99.9997 percent reliability ... means you might hit a misfire every 300,000 rounds.

Over the years, the average is one rejected primer in about every 250,000, but most of the flaws are minor defects or damage such as slightly out-of-round primers that would have no effect on reliability."​

Article attributed most common cause of primer misfires to:

• Insufficient primer cup indent - Primer was not struck with sufficient force from damaged firing pin (bent or chipped tip) or weak/dragging firing-pin spring or dirty/obstructed spring channel.

• Excessive headspace - Straight walled semi-auto cartridge, instead of headspacing off case mouth, shorter case headspace off extractor

• Improper reloading technique - Primer not seated firmly to the bottom of primer pocket moves deeper in the primer pocket when hit by firing pin but anvil tip does not detonate priming compound against the cup

• Shooter/firearm induced misfires - Slide or bolt is not returned to full battery before firing

"... try this demonstration the next time you go to the range. Unload your rifle. Double-check to make sure it is unloaded. Close the bolt, then raise the bolt very slightly. Squeeze the trigger while watching the bolt handle. You can see the bolt handle snap closed. The energy to make that happen is being robbed from the firing-pin velocity and energy normally used to strike the primer."​

• Variations in brands and lot numbers - Different brand and lot of primers can vary in sensitivity and primer cup hardness (often by design or source material)

• Contaminated ammunition - Light penetrating oil and long-term storage in damp conditions or submersion in water can desensitize primers

Since misfires due to a defective primer is rare, if you experience a misfire, investigate above list of possible causes to determine the cause to fix the problem.

 

[Pat Riot]

Thank you, LiveLife.

One other misfire cause:
Hammer springs worn or too light. I have seen this a lot in Cowboy Action Shooting and in other competitive shooting. Somehow it’s always the primer’s fault.

 

[higgite]

"Primers are not perfect — nothing man-made is — but they are very reliable. Statistically, you might encounter a defective primer, if you shoot enough ... 99.9997 percent reliability ... means you might hit a misfire every 300,000 rounds.

I've had one faulty primer out of ??? thousands (far less than 300K). Failed repeated restrikes. Decapped it when I got home and found just a primer cup with compound, but no anvil. Ain't I the lucky one? Winning lottery ticket? No-o-o-o-o! Faulty primer? Of course!

 

[kcofohio]

I've had one faulty primer out of ??? thousands (far less than 300K). Failed repeated restrikes. Decapped it when I got home and found just a primer cup with compound, but no anvil. Ain't I the lucky one? Winning lottery ticket? No-o-o-o-o! Faulty primer? Of course!

I have found an extra anvil in a tray. Maybe it was yours.

 

[higgite]

I have found an extra anvil in a tray. Maybe it was yours.

Now you tell me!

 

[Walkalong]

Copied this from an old post of mine.

Primers need to be seated until the anvil legs touch the bottom of the primer pocket (Minimum), and then a little more so the cup pushes down around the legs, up until it hits the bottom of the primer pocket (Maximum).

If seated to little (Anvil legs not touching the bottom of the primer pocket), the firing pin has to seat it fully and then have enough energy left over to crush the priming compound between the cup and the anvil. Sometimes it does not, these are the ones that so often fire on the second try. The first try seats them fully, the second try fires them.

bds has some great primer pics here somewhere that shows the cup and anvil and how they are positioned with each other prior to seating. The anvil legs are sticking out of the cup just a little bit.

After fully seating the anvil's legs and the primer cup is hard against the bottom of the pocket, it takes a great deal of pressure at this point to damage the primer so much it fails.

It is fairly easy to seat a primer too soft, not fully seating it, so that it misfires, but difficult to seat them so hard it damages them to the point of not firing. This statement is based on my decades of seating primers with various tools. I have never had one fail from being seated to hard/deep. Not saying that with some primer tools and some gorilla grips it can't be done, but it is 100/1000 times less likely to happen than seating one too shallow/soft.

We have threads here all the time when failures to fire end up being primers seated too softly/shallow. I can't remember one where it turned out someone managed to crush a primer into submission. I would suggest to all to try it. Some priming systems simply cannot do it for mechanical reasons. Some might have enough travel to do it if you have the strength, That cup surrounded by the brass primer pocket is tough to crush. Very tough.

 

[Toprudder]

I've had one faulty primer out of ??? thousands (far less than 300K). Failed repeated restrikes. Decapped it when I got home and found just a primer cup with compound, but no anvil. Ain't I the lucky one? Winning lottery ticket? No-o-o-o-o! Faulty primer? Of course!

I had one in which there was no primer compound.